Scientists investigate a novel feed ingredient that enhances shrimp performance

Dr. Alberto J.P. Nunes, Labomar and Tonje E. Dominguez, Aker BioMarine

Maintaining a healthy and thriving shrimp population is essential for the success of any shrimp farm. Farmers seek solutions that pack a nutritional punch to keep their shrimp stocks growing and thriving. It has become the task of scientists to experiment with ingredients, finding the right combination to enhance shrimp growth, health and overall survival. One ingredient stands out from the others in this research, revealing positive results on the shrimp populations tested. This ingredient is Antarctic krill (Euphausia superba) oil.

Astaxanthin krill oil proves to be an effective supplement for shrimp

Shrimp farmers today strive for rapid animal growth and resistance to stress. By seeking shorter production crops with higher annual yields even under environmental challenges, researchers are testing new ways to mitigate the effects of high salinity conditions while still fostering growth. One such solution can be found in astaxanthin krill oil.

Researchers from LABOMAR Instituto de Ciências do Mar, Brazil, have done several interesting studies on the effect of astaxanthin krill oil as a performance supplement to Pacific whiteleg shrimp.

An unpublished study (personal communication) performed a nursery trial in which post-larval (PL) Pacific whiteleg shrimp were fed graded dietary levels (0%, 1%, 3% and 5%) of astaxanthin krill oil (AKO) in a standardized diet to PL in 1-m 3 outdoor tanks for 51 days. After harvest, growth was measured and a stress test was carried out to evaluate shrimp resistance to a

Figure 1. Final body weight (g) and percentage increase in growth of the control and AstaOmega groups.

sudden and acute change to water salinity (drop from 39 g/L to freshwater) and temperature (27.9 to 19.2 ± 0.9 o C). Stress resistance was measured by mortality numbers. The results showed that a minimum of 1% AKO was sufficient to promote an enhanced survival compared to 0% AKO. However, at 5% supplement, no shrimp mortality was recorded after 30 minutes of exposure. Hence, the supplement of AKO at all dietary levels promoted resistance to acute osmotic and thermal stress. At 5% supplement, shrimp also had a significant increase in final body weight.

Another study (Rufino et al., 2020) from the same institute, investigated how supplementing diets for juvenile Pacific whiteleg shrimp under osmotic stress with various oil mixes affected their growth performance. Shrimp at initially 1 gram body weight were reared in fifty 1-m 3 tanks for 75 days under high salinity starting conditions at 42 g/L and descending throughout the test period. They were fed a commercial 38% crude protein feed top-coated with 1-3% astaxanthin krill oil (AKO) and/or soybean oil (SBO) (0AKO-3SBO, 1AKO-2SBO, 2AKO-1SBO, and 3AKO-0SBO%). The results showed that shrimp significantly improved their growth performance when a mix of AKO and SBO were supplemented to the commercial feed. The top coating of a supplementary oil mix consisting of 1% AKO and 2% SBO to a finished grower feed improved shrimp final body weight and yield at normal salinity. However, under longer exposure periods to hypersalinity in enclosed tanks, a minimum of 2% AKO mixed with 1% SBO was required to increase weight gain. Shrimp survival was unaffected by oil supplements.

Finally, a study published in 2018 analyzed the effects of astaxanthin krill oil when supplemented into a grower diet of the Pacific whiteleg shrimp. They compared the effects on growth of different oil sources – soybean (SBO), fish (FO) and astaxanthin krill oil (AKO) (at 3 and 5 % inclusion rate) when used under ideal or high salinity conditions. They also looked at important sensory parameters for end-consumer like color, flavor and shrimp tail texture. Juvenile shrimp were placed in ideal water salinity (22 ± 0.4 g/L) or high water salinity (41 ± 0.4 g/L) over 64 days and fed a diet with similar nutrient levels, though differing in their essential fatty acid intake due to the varying oils. After 64 days, the final body weight of the shrimp placed in ideal salinity conditions was 4% higher in the AKO group compared to the FO.

The results showed that the shrimp in high water salinity conditions grew the least when fed the SBO and FO diets, as expected since higher water salinity typically reduces the final body weight of shrimp. However, the shrimp fed the AKO resulted in a final body weight that was significantly higher than the other two test groups (Fig. 1), and 10% higher than the SBO group.

Furthermore, scientists found that shrimp given the AKO had significantly higher consumer preference for

Figure 2. Values represent the sum of best-worst evaluation of 20 panelists (n=60) for each sample.

color and flavor than the two other oil groups (Fig. 2). Finally, shrimp fed AKO or FO diets showed a higher percentage of EPA and DHA in the shrimp tail fatty acid profile at harvesting regardless of the salinity.

The overall conclusion was that astaxanthin krill oil at 5% inclusion rate is effective in enhancing final growth, improving shrimp tail color and shrimp flavor, as well as the fatty acid composition of the Pacific whiteleg shrimp in all tested water conditions.

A supplement with many strengths and more to be uncovered

Astaxanthin krill oil can be classified as an all-natural specialty performance supplement made from Antarctic krill. It is rich in the omega-3 fatty acids, EPA and DHA as well as the powerful antioxidant and colorant astaxanthin, and positively impacts growth, stress resistance and color of shrimp, particularly in early growth stages where these are essential nutrients. In addition to this, the astaxanthin krill oil might have even more benefits. Nutrients like omega-3 and astaxanthin can be retrieved from other commodity ingredient sources, however preliminary trial results from unpublished studies might suggest that the combination and chemical form of which nutrients are found in astaxanthin krill oil can be of importance. It has also shown to be a powerful feed attractant. More research is needed to establish possible synergies and effects of astaxanthin krill oil, but it is certainly an interesting supplement for shrimp hatcheries and can be used in different ways, such as during feed manufacturing, as top coating for dry feed and mixed with fresh food. The astaxanthin oil in the studies mentioned is MSC-certified and produced by Aker Biomarine, a sustainable harvester of Antarctic krill. Antarctic krill fishery has received an “A” rating for its well-managed fishery from the Sustainable Fisheries Partnership (SFP) and is ensured strict catch limits by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).

Hence, it could be a natural and sustainable choice for shrimp farmers seeking rapid growth among a healthy shrimp population.

References available by request

More information: Alberto J. P. Nunes

Professor LABOMAR, Universidade Federal do Ceará, Brazil E: alberto.nunes@ufc.br

Tonje E. Dominguez

Director Specialty Animal Nutrition Products Aker BioMarine Antarctic AS, Norway E: Tonje.Dominguez@akerbiomarine.com